396 CONSIDERATION OF CARBON COMPOUNDS. 



Determination of the total alkaloids and of quinine in Cinchona. The 

 U. S. P. has adopted the following method for the assay of cinchona : 



1. For total alkaloids. To 20 grammes of finely-powdered cinchona, and 

 contained in a glass-stoppered flask, add 200 c.c. of a previously prepared mix- 

 ture of 19 volumes of alcohol, 5 volumes of chloroform, and 1 volume of 

 ammonia water ; shake the mixture frequently during four hours. Then filter 

 into a bottle through a funnel containing a pellet of cotton, in such a manner 

 that no material loss by evaporation may result. Transfer 100 c.c. of the 

 filtrate to a beaker and evaporate to dryness. Dissolve the residue of crude 

 alkaloids thus obtained in 10 c.c. of water and 4 c.c. of normal sulphuric acid ; 

 with the aid of a gentle heat, filter the cooled solution into a separatory funnel, 

 and wash the beaker and filter until the filtrate no longer has an acid reaction, 

 using as small a quantity of water as possible. Now add 5 c.c. of normal 

 potassium hydrate, or such an amount as will render the liquid decidedly 

 alkaline, and extract the alkaloids by shaking the mixture, first with 20 c.c., 

 and then repeatedly with 10 c.c. of chloroform, until a drop of the last chloro- 

 form extraction, when evaporated on a watch-glass, no longer leaves a residue. 

 Evaporate the chloroformic extracts in a tared beaker, dry the residue at 

 100 C. (212 F.), and weigh. The weight found, multiplied by 10, will give 

 the percentage of total alkaloids. 



2. For quinine. Transfer 50 c.c. of the clear filtrate remaining over from the 

 preceding process to a beaker, evaporate it to dryness, and proceed as directed 

 in the assay for total alkaloids, using, however, only one-half the amounts of 

 volumetric acid and alkali there directed Add the united chloroformic 

 extracts gradually, and in small portions at a time, to about 5 grammes of 

 powdered glass contained in a porcelain capsule placed over a water-bath. 

 After the chloroform has been expelled moisten the residue with ether, and, 

 having placed a funnel containing a filter of a diameter of 7 centimeters, and 

 well wetted with ether, over a small graduated tube (A), transfer to the filter 

 the ether-moistened residue from the capsule. Rinse the latter several times 

 with fresh ether, so as to transfer the whole of the residue to the filter, then 

 percolate with ether, drop by drop, until 10 c.c. of percolate have been obtained. 

 Then collect another percolate of 10 c.c. by similar slow percolation with ether, 

 in a second graduated tube (B). Transfer the contents of the two tubes com- 

 pletely (using ether for washing) to two small, tared capsules (marked A and 

 B), evaporate at 100 C. (212 F.) and weigh them. From the weight of residue 

 obtained in A deduct that contained in B, and multiply the remainder by 

 twenty. The product represents, approximately, the percentage of quinine, 

 containing one molecule of water. 



The explanation of the above processes is this : By the action of ammonia 

 water the cinchona alkaloids are set free and become dissolved in the alcoholic 

 chloroform used for extraction of the bark. The liquid also acts, however, as 

 a solvent upon other substances, for which reason the impure alkaloids are 

 purified by dissolving the mass in acidified water, liberating the alkaloids by 

 caustic potash and extracting them by means of chloroform. 



While the direct evaporation of this chloroform solution gives the weight of 

 the total alkaloids, a separation of quinine from the other cinchona alkaloids 

 is accomplished by ether, in which quinine is much more soluble than the rest 

 of the alkaloids. In order to accomplish the extraction with ether successfully 



